ERS-2 was launched almost 30 years ago as the most sophisticated Earth observation object. (Photo: Reproduction)
A European satellite weighing 2.3 tons uncontrolled re-entered the Earth’s atmosphere last Wednesday (21), and fell over the Pacific Ocean, between Alaska and Hawaii, in the United States. ERS-2 was launched almost 30 years ago as the most sophisticated Earth observation object.
The European Space Agency’s expectation that it would disintegrate almost completely during reentry, 80 km above the Earth’s surface, was fulfilled. “It was not possible to control ERS-2 at any time during its reentry and the only force that drove its descent was unpredictable atmospheric drag,” says the statement.
The uncontrolled entry happens because ERS-2 consumed the last of its fuel in 2011 to minimize the risk of a catastrophic explosion that could have generated a large amount of space debris. Since then, its batteries were already discharged and its communications antenna and on-board electronics were turned off. In other words, there was no longer any way to actively control the satellite’s movement from the ground during its descent.
The unpredictability of natural re-entries is due to the limited ability to predict the density of the layers of the Earth’s atmosphere. They are what will produce the drag responsible for the decay of the satellite’s orbit – the denser they are, the more drag they generate and the faster the satellite’s orbit decays.
However, density predictions depend on the atmospheric model used and unpredictable solar activity. Other aspects that affect the speed of orbital decay, such as which direction the satellite is facing and therefore what surface area is exposed to the atmosphere, cannot be determined simply by monitoring the satellite’s trajectory.
ERS-2 was launched on April 21, 1995. At the time, it was the most sophisticated Earth observation spacecraft ever developed and launched by Europe. Together with the almost identical ERS-1, it collected valuable data on Earth’s land surfaces, oceans and ice caps and was called upon to monitor natural disasters such as severe floods or earthquakes in remote parts of the world.
According to the European Space Agency, the annual risk of a human being injured by space debris is very low. For comparison purposes, it is 1.5 million times lower than the risk of dying in a domestic accident; 65 thousand times lower than the risk of being struck by lightning; and three times lower than the risk of being hit by a meteorite.
2024-02-25 22:00:58
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